You're making some sense there. I've never understood why "platform longevity" is such a big thing for some people. By the time you actually need a CPU upgrade, you most probably have to change your motherboard as well, whether Intel or AMD. Sure, AM4 has been around for a very long time, so you could potentially upgrade an 1800X to a 5800X3D, but chipset vs CPU compatibility wasn't always flawless. If memory serves, it took AMD something like a year to figure out Ryzen 5000 support on older chipsets, so if you wanted such an upgrade, you probably got a new board anyway.
On the other hand, if you want a CPU upgrade with every generation, then saving money isn't your main motivation in the first place.